Filter pad



Nov. 29, 1938. H. M. GAARDER FILTER PAD Patented Nov. 29, 1938 UNITED STATES PATENT CFFICE FILTER PAD Ware Application september 25, 1936, serial No. itam 4 Claims.

'Ihis invention relates to an improved air filter pad, and more particularly to a filter pad prepared of loosely aggregated fibrous material.

Air lters of the impingement type which remove dirt, dust, pollen and bacteria from gases by impingement, as distinguished from a straining process, have hitherto been customarily prepared and marketed in metal or cardboard containers. These containers are normally of the size of the opening in which the filter is to be employed, and the filtering medium fits inside of them as closely as possible. Such covers are made as open as possible, but still decrease the filtering area about or more, because they l5 cover three-fourths of an inch to an inch at the edges and cover both the face and back of the filter to a considerable degree.

By means of the present invention, an oversized pad is prepared with resilient edges, which 20 compress against the sides of the filter frame and provide a dust-tight seal on all sides. At the same time, the edges of the iilter are left uncovered, providing a maximum exposure of the surface.

The invention is illustrated in the drawing, in

which- Fig. 1 is a face view of a filter; and

Fig. 2 is a section of the line 2 in Fig. 1.

As illustrated in the drawing, the lter comprises a mass of fibrous material l0 between a top screen ill and a bottom screen l2, of very coarse mesh grid, the fibrous material extending beyond the edges, as indicated at i3. The top and bottom screens are joined and, at the same time, rigidly separated by pins or posts i6, which are welded to the lower screen and are provided with open hooks l5, which in assembling of the pad are passed over the upper grid and closed, as indicated at I6.

As an example of the invention, an air filter was produced by filling a square mold 201/4 inches on edge and about two inches thick with approximately seven to eight .ounces of hair. The hair is' preferably hog hair, which may include minor proportions of uncurled hair, say 7 to 25% of small amounts, up to 10% of long hair, such as cattle hair, horse tail hair, or horse mane hair. The uncurled hair may be either intermixed with curled hair, or may be evenly distributed on one face of the filter, for example, the air exit face. The hair should be ufied in order to provide proper density ratios, which should ordinarily fourth ounces. A thin pad, of course, is preferably more dense than a thick one, and with shorter hair the ydensity ranges may be somewhat higher. The loosely formed pad is then treated with an adhesive to bind the outer hairs firmly together, 5 for example, by spraying the formed pad with an adhesive. The screens are then applied, one at the top and one at the bottom, and are anchored together. A preferred grid comprises openwork wires, for example, 14-gauge galvanized iron wire, 10 spaced at approximately three-inch intervals and spot-welded at the junctions. For example, in a 19% inch screen, the grid may be made up on five equally spaced wires of this type in each direction and are joined at the edges to a 12- 15 gauge galvanized wire frame, slightly curved at the corners. The posts or pegs are preferably spotwelded to the frame at appropriate intervals about its edge, and the hooks are passed over the upper screen by compression of the pad and 20 may then be clamped over the upper frame. With a 19V; inch frame, as indicated, eight posts distributed as indicated in Fig. 1 and made of 14- gauge wire are satisfactory. Posts may be supplied within the filter, if desired, particularly 25 upon larger filters, but with filters up to 20 inches or even larger, such internal posts are not necessary for ordinary use.

After the screens have been applied and fastened together, the hairs may be coated with a 30 tacky or dust-collecting material of the usual type, either by dipping or spraying. This opera-- tion may be performed, if desired, before the grids are applied.

A pad prepared in this manner preferably is 35 so made so that the hair extends one-quarter to three-quarters of an inch, and preferably about one-half inch, beyond the edges of the frame l1. Where the hair is resilient, as with hog hair, this provides a very eiective dust seal when placed in 40 a supporting frame, inasmuch as the frame il is only slightly smaller than the size of the frame in which the filter -is to be placed. At the same time, Ythe .entire face of the filter is available for air filtering, increasing the available area 45 about 20%, as compared with ordinary filters. The filter is also suiciently rigid to permit tapping thereof face down to remove dust, without injury to the filter medium. The large mesh of the grids likewise aifords practically no resist- 50 ance to air passing through the filter. The posts shown are readily removable by opening of the hooks i6, and the grids may be removed from a dirt-filled pad and placed on a clean one.

While the filter has been described as being of hair, other brous material, and particularly other ber which is naturally or artiiicially 1resilient, may be employed.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary` limitations should be understood therefrom,but the appended' claims should be construed as broadly as permissible, in view of the prior art.

I claim:

1. An air iilter of theimpingement type comprising a at pad of loosely distributed resilient brous iltering material, a coarse mesh screen support of less cross-section than the pad, the edges of said pad extending substantially uniformly approximately one quarter to three quarters oi' an inch beyond the edges of the support, the resiliency of the fibers being such as to provide an edge'seal having substantially the ltering capacity and low air resistance oi the body of the iliter, and said support being slightly smaller and the pad slightly larger than the passageway for which the pad is intended.

2. A pad as set forth in claim 1 in which the outer iibers oi' the pad are bound nrmly together with adhesive.

3. A pad as set forth in claim 1 in which the ilber is predominantly hog hair.

4. An air filter pad of the impingement type comprising a iiat pad of loosely distributed resilient iibx'ous filtering material. a coarse mesh screen support of less cross-section than the pad,

f the edges of said pad extending substantially uniformly beyond the edges of the screen, the resiliency ot the iibers and the width of said extension being such as to provide an edge seal having substantially the ltering capacity and low air re- A sistance of the body of the filter, and said support being slightly smaller and the pad slightly larger t the f t eway for which the pad is intended. 

